The present invention relates generally to thermal devices and more particularly to thermal devices with multiple thermoelectric loads.
Thermal devices are used to control the temperature of an environment, within which a sample may reside. For example, one type of thermal device is a thermal cycler that can regulate the temperature of a biological or chemical reaction, such as a Polymerase chain reaction (PCR). In some reactions, the temperature must be raised or lowered in discrete, pre-programmed steps. Thus, the devices must be able to cool and heat a sample.
To provide heating and cooling, some thermal devices use thermoelectric cooling. Thermoelectric coolers or heat pumps use the Peltier effect to create a heat flux between the junctions of two different types of materials. The Peltier effect occurs when a current is passed through two dissimilar metals or semiconductors (n-type and p-type) that are connected to each other at two junctions (Peltier junctions). The applied current drives a transfer of heat from one junction to the other, cooling one junction while the other heats up. The direction of heat transfer is controlled by the polarity or direction of the applied current; reversing the polarity changes the sign of the heat absorbed/evolved. The heat gradient is proportional to the amount of current though the device.
Some thermal cyclers are equipped with multiple blocks and/or wells to allow several different reactions to be carried out simultaneously. Also, some apparatuses have a gradient function, which allows different temperatures indifferent parts of a block. Both configurations can utilize multiple Peltier junctions or loads, which may also be used to help achieve uniformity in temperature.
To provide both polarities of current, thermoelectric devices employ numerous power components to control the flow of current. Power components are typically the most expensive components in any type of amplifier design. Additionally, the number of power components is increased by having multiple thermoelectric (Peltier) loads.
Accordingly, it is desirable to provide circuits, methods, and systems for controlling the current to multiple loads while minimizing the number of power components.